The placenta of the pig

Frieß, A. E.; Sinowatz, Fred; Skolek-Winnisch, Rita; Träutner, W

doi:10.1007/bf00315905

Cited by 117 publications

(26 citation statements)

References 13 publications

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“…2 tial, probably developed from the noninvasive epitheliochorial placenta observed in nonruminant artiodactyls, such as camels (32) and pigs (33). The calculation of 52 Ϯ 6 million years for the origin of the binucleate cell-specific PAGs is only slightly lower than recent estimates for the divergence of the Ruminantia and the Suidae (26).…”

Section: Discussionmentioning

confidence: 79%

Adaptive diversification within a large family of recently duplicated, placentally expressed genes

Hughes

Green

Garbayo

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

110

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The pregnancy-associated glycoproteins (PAG) are putative peptide-binding proteins and products of a large family of genes whose expression is localized to the placental surface epithelium of artiodactyl species. We have tested the hypothesis that natural selection has favored diversification of these genes by examining patterns of nucleotide substitution in a sample of 28 closely related bovine, caprine, and ovine family members that are expressed only in trophoblast binucleate cells. Three observations were made. First, in codons encoding highly variable domains of the proteins, there was a greater accumulation of both synonymous and nonsynonymous mutations than in the more conserved regions of the genes. Second, in the variable regions, the mean number of nonsynonymous nucleotide substitutions per site was significantly greater than the mean number of synonymous substitutions per site. Third, nonsynonymous changes affecting amino acid charge occurred more frequently than expected under random substitution. This unusual pattern of nucleotide substitution implies that natural selection has acted to diversify these PAG molecules at the amino acid level, which in turn suggests that these molecules have undergone functional diversification. We estimate that the binucleate cell-expressed PAG originated 52 ؎ 6 million years ago, soon after the divergence of the ruminant lineage. Thus, rapid functional diversification of PAG expressed in trophoblast binucleate cells seems to have been associated with the origin of this unique placental adaptation.aspartic proteinase ͉ multigene families ͉ positive selection ͉ trophoblast ͉ pregnancy-associated glycoprotein

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Section: Discussionmentioning

confidence: 79%

Adaptive diversification within a large family of recently duplicated, placentally expressed genes

Hughes

Green

Garbayo

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

110

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“…Capillaries on the maternal and fetal sides come within a few microns of each other (Fig. 5A), often squeezing down to the tight junctions between the trophoblast cells on the one side and uterine epithelial cells on the other, probably allowing efficient exchange of small molecules (Friess, et al 1980). Movement of macromolecules that carry essential components such as metals and vitamins, is more problematic, but there an alternative strategy has been employed, namely the delivery of these components, not in the blood but in uterine secretions, a process called histotrophic nutrition (Fig.…”

Section: Mammalsmentioning

confidence: 99%

“…Maternal capillaries (MC) are placed just below the basal lamina of the UE; D, A general view of a dome-shaped areola (AE) situated above the mouth of a uterine gland (UG) at d 30 of pregnancy. Figures 5A-C are from Friess et al (1980) (Friess, et al 1980); Figure 5D is from Friess et al (1981)(Friess, et al 1981) with permission.…”

Section: Figurementioning

confidence: 99%

The evolution of the placenta

Roberts¹,

Green²,

Schulz³

2016

Reproduction

174

125

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The still apt definition of a placenta is that coined by Mossman, namely apposition or fusion of the fetal membranes to the uterine mucosa for physiological exchange. As such it is a specialized organ whose purpose is to provide continuing support to the developing young. By this definition, placentas have evolved within every vertebrate class other than birds. They have evolved on multiple occasions, often within quite narrow taxonomic groups. As the placenta and the maternal system associate more intimately, such that the conceptus relies extensively on maternal support, the relationship leads to increased conflict that drives adaptive changes on both sides. The story of vertebrate placentation, therefore, is one of convergent evolution at both the macro- and molecular levels. In this short review, we first describe the emergence of placental-like structures in non-mammalian vertebrates and then transition to mammals themselves. We close the review by discussing mechanisms that might have favored diversity and hence evolution of the morphology and physiology of the placentas of eutherian mammals.

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“…In order to maintain sufficient surface area for fetal–maternal exchange, a folded trophoblast/endometrial epithelial bilayer is developed. The trophoblast/endometrial surface area for the maternal-fetal exchange significantly increase from gestational days 35 to 70, coinciding with the rapid growth of the pig fetus [5], [6]. The porcine uterine epithelium is intact throughout pregnancy [7] and the uterine endometrium exhibits characteristic morphological and functional changes, which functions in supporting and nurturing the developing conceptuses during pregnancy.…”

Section: Introductionmentioning

confidence: 99%

Expression Patterns of MicroRNAs in Porcine Endometrium and Their Potential Roles in Embryo Implantation and Placentation

Liu

Cheng

et al. 2014

PLoS ONE

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Implantation and placentation are critical steps for successful pregnancy. The pig has a non-invasive placenta and the uterine luminal epithelium is intact throughout pregnancy. To better understand the regulation mechanisms in functions of endometrium at three certain gestational stages that are critical for embryo/fetal loss in pigs, we characterized microRNA (miRNA) expression profiles in the endometrium on days 15 (implantation period), 26 (placentation period) and 50 (mid-gestation period) of gestation. The differentially expressed miRNAs across gestational days were detected and of which, 65 miRNAs were grouped into 4 distinct categories according to the similarities in their temporal expression patterns: (1) categories A and B contain majority of miRNAs (51 miRNAs, such as the miR-181 family) that were down- or up-regulated between gestational days 15 and 26, respectively; (2) categories C and D (14 miRNAs) consist miRNAs that were down- or up-regulated between gestational days 26 and 50, respectively. The expression patterns represented by eleven miRNAs were validated by qPCR. The majority of miRNAs were in categories A and B, suggesting that these miRNAs were involved in regulation of embryo implantation and placentation. The pathway analysis revealed that the predicted targets were involved in several pathways, such as focal adhesion, cell proliferation and tissue remolding. Furthermore, we identified that genes well-known to affect embryo implantation in pigs, namely SPP1, ITGB3 and ESR1, contain the miR-181a or miR-181c binding sites using the luciferase reporter system. The present study revealed distinctive miRNA expression patterns in the porcine endometrium during the implantation, placentation or mid-gestation periods. Additionally, our results suggested that miR-181a and miR-181c likely play important roles in the regulation of genes and pathways that are known to be involved in embryo implantation and placentation in pigs.

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The placenta of the pig

Cited by 117 publications

References 13 publications

Adaptive diversification within a large family of recently duplicated, placentally expressed genes

Adaptive diversification within a large family of recently duplicated, placentally expressed genes

The evolution of the placenta

Expression Patterns of MicroRNAs in Porcine Endometrium and Their Potential Roles in Embryo Implantation and Placentation

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